1. Field of the Invention
The present invention relates to a liquid ejection head from which a liquid is ejected and a process for producing the liquid ejection head.
2. Description of the Related Art
As an example of a liquid ejection head, an ink jet recording head ejecting a liquid such as an ink for use in recording is known. A general ink jet recording head has a recording element substrate in which a flow-path-forming member capable of ejecting an ink droplet from a liquid ejection orifice by an energy-generating element for applying ejection energy to a liquid is joined to a principal plane of the substrate, and an electric wiring board for applying an electric signal to the recording element substrate.
On the substrate surface to which the flow-path-forming member is joined, an electrothermal converter of a heating resistor is provided as the energy-generating element. An ink is heated by the electrothermal converter within the flow-path-forming member and ejected as an ink droplet from the liquid ejection orifice by the action of film boiling. A system in which an ink droplet is ejected by using an electricity-pressure converter such as a piezoelectric element in place of the electrothermal converter is also known.
The surface on the side opposite to the flow-path-forming member of such a substrate is joined to an ink tank, and an ink supply path through which an ink within the ink tank is supplied to a flow path of the flow-path-forming member passes through the substrate from this surface.
With respect to such a conventional ink jet recording head, Japanese Patent Application Laid-Open No. 2012-187804 discloses a method capable of reducing a possibility that a recording element substrate may be broken by a temperature or humidity cycle and a possibility that an ink may leak from a boundary surface between an ink tank and a recording element substrate which are joined to each other.
According to the recording head described in Japanese Patent Application Laid-Open No. 2012-187804, a depressed portion in which the recording element substrate is housed with a plane on which a liquid ejection orifice is formed (referred to as an ejection orifice face) facing to the outside is formed in the ink tank to which the recording element substrate is joined. A bottom surface of the depressed portion has an ink supply port communicating with an opening of an ink supply path exposed to a back surface of the recording element substrate and a principal plane which is present around the ink supply port and is joined to the back surface of the recording element substrate with an adhesive. An electric connection portion connecting an electric wiring board is provided at an end portion of the ejection orifice face.
The recording element substrate is provided with a plurality of side surfaces including a side surface of a non-electric connection side formed on a side on which the electric connection portion of the ejection orifice face is not provided and a side surface of an electric connection side formed on a side on which the electric connection portion of the ejection orifice face is provided.
This recording element substrate is joined to the ink tank at the principal plane located at the bottom surface of the depressed portion through an adhesive. A sealing material is filled into a space between the side surface of the electric connection side and a side wall of the depressed portion, and the electric connection portion is also sealed with the sealing material. On the other hand, between the side surface of the non-electric connection side and a side wall of the depressed portion, the sealing material only covers an external surface of an adhesive exposed from between the back surface of the recording element substrate and the bottom surface of the depressed portion over the whole length thereof, and most of the side surface of the non-electric connection side is exposed without being covered with the sealing material.
According to such a method, the sealing material is filled into only a partial space corresponding to the side surface of the electric connection side of the recording element substrate without filling all the spaces between the respective side surfaces of the recording element substrate and the side walls of the depressed portion with the sealing material. Therefore, it is expected that the breakage of the recording element substrate by the temperature or humidity cycle is hard to occur.